An unmanned spacecraft is in a circular orbit around the moon, observing the lunar surface from an altitude of 56.0 km. To the dismay of scientists on earth, an electrical fault causes an on-board thruster to fire, decreasing the speed of the spacecraft by 16.0 m/s. If nothing is done to correct its orbit, with what speed (in km/h) will the spacecraft crash into the lunar surface? I tried finding the velocity to keep it in orbit, subtracted the decrease in speed, found the new radius and then found the new velocity it crashes with, but it is wrong. can anyone help?